Various polymeric coatings and articles are produced in processes involving the use of organic solvents. There is an intense effort by law makers, researchers, and industry to promote high and 100% solids formulations to reduce or eliminate the use of such solvents and the attendant costs and environmental contamination. These processes require a latent catalyst or latent reaction promoter which can be activated in a controlled fashion.
Curing of polyurethane precursors using reaction promoters such as tin salts or tertiary amines is known in the art. Curing of polymerizable mixtures of polyisocyanates with polyols (referred to as polyurethane precursors) using latent catalysts is known in the art (see for example U.S. Pat. Nos. 4,521,545, and 4,582,861).
Photocuring of urethane (meth)acrylates is well known (see T. A. Speckhard, K. K. S. Hwang, S. B. Lin, S. Y. Tsay, M. Koshiba, Y. S. Ding, S. L. Cooper J. Appl. Polymer Science 1985,30, 647-666. C. Bluestein Polym.-Plast. Technol. Eng. 1981,17 83-93). Photocuring of polyurethane precursors using diazonium salts, tertiary amine precursors, or organotin compounds is also known (see U.S. Pat. Nos. 4,544,466, 4,549,945, and EP No. 28,696, Derwent abstract). All of these methods suffer from one or more of the following disadvantages: sensitivity to oxygen, requirement of ultraviolet and/or high intensity light, need for modified resins, loss or dilution of urethane properties, low activity, excessive cure time, poor solubility, and poor potlife.
The photocure of urethane prepolymers using a latent organometallic salt as catalyst is described in U.S. Pat. No. 4,740,577 and U.S. Pat. No. 5,091,439. Energy polymerizable compositions comprising, for example, an ethylenically-unsaturated monomer and polyurethane precursors and as a curing agent, a latent organometallic salt, has been disclosed in EP 344,911. Polyisocyanate coatings are disclosed to be cured in the presence of a ferrocenium compound in U.S. Pat. No. 4,861,806.
An ethylenically unsaturated monomer in combination with polyurethane precursors or cationically polymerizable monomers have been disclosed in U.S. Pat. No. 4,950,696 to be cured by an organometallic compound with an onium salt.
U.S. Pat. No. 4,342,793 teaches curable compositions containing polyurethane precurosrs and free radically polymerizable compounds, using, for example, tin salts, tin compounds, or tertiary amines to cure the polyurethane precursors, and organic peroxides (including hydroperoxides, per acids, per esters, and dialkyl peroxides), azo compounds, or free radical initiators such as benzoin, benzoin ethers, Michler's ketone, or chlorinated polyaromatic hydrocarbons to cure the free radically polymerizable compounds. Use of organometallic salts with hydroperoxides or acyl peroxides to cure polyurethane precursors with or without ethylenically unsaturated compounds is not taught.
International Patent document WO 88/02879 Loctite Corporation describes the use of a free radical polymerization initiator with a .pi.-arene metal complex to cure a free radically polymerizable monomeric material The free radically polymerizable material is further described as one or more monomers and/or prepolymers containing acrylate or methacrylate groups; or a copolymerizable monomer combination based on a polythiol and a polyene. The free radical polymerization initiator is specified as being most suitably, benzoyl peroxide, cumene hydroperoxide, methyl ethyl ketone peroxide and the like. This reference does not disclose urethane precursors as polymerizable materials.
Australian Pat. Document 38551/85 relates to a hardenable composition consisting of a) a material polymerizable by cationic or free radical polymerization, b) an iron(II)-.eta..sup.6 -benzene-.eta..sup.5 -cyclopentadienyl complex salt, c) a sensitizer for the compounds b), and d) an electron acceptor as an oxidizing agent for the material polymerizable by free radical polymerization, wherein the oxidizing agent is a hydroperoxide.
U.S. Pat. No. 4,985,340 describes an energy polymerizable composition that includes, for example, urethane precursors that may or may not be combined with ethylenically-unsaturated monomers and use as curing agent a combination of an organometallic salt and an onium salt. The use of peroxide as a free radical source is not taught.
Organometallic complex cations have been described (see European Patent Nos. 094,915 (1983) (Derwent Abstract); and 094,914 (1983) (Derwent Abstract); and U.S. Pat. No. 5,089,536. Energy polymerizable compositions comprising ionic salts of organometallic complex cations and cationically sensitive materials and the curing thereof has been taught.
Recently discovered preparations of cyclopentadienyliron(II)arenes have been disclosed in U.S. Pat. No 5,059,701.
Use of an organometallic salt or diazonium salt with a free-radical photoinitiator which can be a peroxide to sequentially cure an energy polymerizable composition consisting of one or more free-radically polymerizable monomers and polyurethane precursors is described in U.S. Ser. No. 07/568,088 (1990). Use of an organometallic salt with a free-radical photoinitiator, which can be a peroxide, in a similar composition and similar method is disclosed in U.S. Ser. No. 07/578,022 to be a pressure-sensitive adhesive These applications do not teach the use of an organometallic salt with a specific peroxide to cure polyurethane precursors with or without ethylenically unsaturated monomers.